Brake Hose–Field Failure Elimination

In LCV segment vehicles were reported for complaint on Spongy brake pedal. In brake assembly parts constitutes of Brake oil reservoir, Rubber brake hose, TMC cylinder and etc. In this study assembly wise and material wise investigations on failed samples were analyzed to understand and resolve the issue. In common these kind of failures can be caused due to contamination of brake fluid, improper material grade usage and also sometimes by assembly issues. Issue identified as that the brake hose in the assembly hardened and not meeting as per the drawing material grade specifications. The plasticizer from brake hose is leaching out to the brake oil and contaminated oil, passes through the TMC cylinder and making EPDM seals to swell. Because of swelling the seal is not seating properly in the groove which results in poor pressure build up in TMC and subsequent spongy brake observed. This study revealed the Improper selection of EPDM grade for the brake hose. Keywords: Brake hose, Field failure, LCV segment vehicles, failure elimination, Tear Down Analysis, Thermo Gravimetric Analysis